1. Field
One embodiment of the invention relates to an electronic device including a casing made of metal, for example, including a structure of a boss provided in the casing.
2. Description of the Related Art
Recently, a trend of thinning a casing of an electronic device such as a portable computer steadily continues. Many casings of electronic devices are made of resin. If the casing is to be further thinned in the future, it will be impossible to secure a desired rigidity for this casing. Therefore, attention has been paid to attempting to fabricate a casing of metal, such as an Mg alloy.
Jpn. Pat. Appln. KOKAI Publication No. 2003-347755 discloses a casing structure of a portable telephone featured in that the casing is made of an Mg alloy, which therefore enhances the electromagnetic wave-shielding function. The casing structure includes a printed wiring board housed in the casing, and a grounding spring connected at one end thereof to a grounding pattern of the printed wiring board and at the other end to the Mg alloy casing. The casing contains a pair of bosses that are placed on both sides of the printed wiring board. Those bosses are fastened to the printed wiring board by screws.
Various circuit components, such as a CPU and a north bridge, are mounted on the printed wiring board to be housed in the casing. Those circuit components generate heat when the device is in operation, which therefore heats the printed wiring board. In the casing structure, the bosses provided on the metallic casing are in contact with the printed wiring board. With such a structure, heat is transferred from the printed wiring board through the bosses to the casing, so the temperature of the casing will possibly rise. If the casing becomes too hot, a user cannot comfortably use the electronic device.